Fix argument detection for shapes

Currently, if a value is passed to `shape()` that cannot be resolved,
such as in `shape(Child.propTypes)`, docgen returns

"type": {
  "name": "shape",
  "value": "unkown"
}

Regardlessly of the typo, this behavior is not in line with the behavior
of other types. Now, the following structure will be returned instead:

"type": {
  "name": "shape",
  "value": "Child.propTypes",
  "computed": true
}

Fixes #87.

Author: fkling

src/__tests__/__snapshots__/main-test.js.snap

@@ -56,3 +56,28 @@ Object {
   }
 }
 `;
+
+exports[`main fixtures processes component "component_4.js" without errors 1`] = `
+Object {
+  "description": "",
+  "methods": Array [],
+  "props": Object {
+    "child": Object {
+      "description": "",
+      "required": true,
+      "type": Object {
+        "computed": true,
+        "name": "shape",
+        "value": "Child.propTypes"
+      }
+    },
+    "something": Object {
+      "description": "",
+      "required": true,
+      "type": Object {
+        "name": "string"
+      }
+    }
+  }
+}
+`;

src/__tests__/fixtures/component_4.js

@@ -0,0 +1,26 @@
+/*
+ *  Copyright (c) 2015, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+/**
+ * Testing computed argument passed to shape()
+ */
+
+import React from 'react';
+
+var pt = React.PropTypes;
+
+class Parent extends React.Component {
+  static propTypes = {
+    something: pt.string.isRequired,
+    child: pt.shape(Child.propTypes).isRequired
+  }
+}
+
+export default Parent;

src/utils/__tests__/getPropType-test.js

@@ -125,6 +125,13 @@ describe('getPropType', () => {
         },
       },
     });
+
+    // computed
+    expect(getPropType(expression('shape(Child.propTypes)'))).toEqual({
+      name: 'shape',
+      value: 'Child.propTypes',
+      computed: true,
+    });
   });
 
   it('resolves variables to their values', () => {

src/utils/getPropType.js

@@ -81,7 +81,7 @@ function getPropTypeObjectOf(argumentPath) {
 }
 
 function getPropTypeShape(argumentPath) {
-  var type: PropTypeDescriptor = {name: 'shape', value: 'unknown'};
+  var type: PropTypeDescriptor = {name: 'shape'};
   if (!types.ObjectExpression.check(argumentPath.node)) {
     argumentPath = resolveToValue(argumentPath);
   }
@@ -101,6 +101,11 @@ function getPropTypeShape(argumentPath) {
     type.value = value;
   }
 
+  if (!type.value) {
+    type.value = printValue(argumentPath);
+    type.computed = true;
+  }
+
   return type;
 }